The invention relates to a method for feeding reaction gas such as oxygen-enriched gas meant for oxidizing the pulverous fuel of a furnace, advantageously a flash smelting furnace, and a possible gaseous extra fuel into the furnace and to adjusting the supply in a concentrate burner. The invention is also related to an apparatus designed for realizing the adjusting, i.e. a multipurpose burner.
The pulverous material itself can be easily dispersed and distributed in the reaction shaft of the furnace in a desired fashion, for instance by means of a central jet distributor which is described in the GB patent 1,569,813.
The turning of oxygen or oxygen-enriched gas such as air from mainly horizontal plane to vertical plane, which is necessary for a vertical reaction shaft for instance in a flash smelting furnace, and the directing thereof to be parallel to the vertical reaction shaft, can also be realized with a directional burner, which is described for instance in the U.S. Pat. No. 4,392,885.
In a normal case, i.e. in a case where air or partially oxygen-enriched air is used, and the fluctuations of capacity are not large, this burner with a stationary aperture is sufficient, but because the tendency nowadays is to use technical grade oxygen of nearly 100%, the gas amounts in the burner are decreased, relatively speaking, down to a fifth. Now the reaching of a certain velocity for the burner gas requires an increasingly small cross-sectional area of flow for the supply orifice of the burner.
Because the orifice most often is annular in shape, the orifice aperture easily becomes small, and even a minor asymmetry in the installation cause the gas flow to pull on one side of the reaction shaft and leads to irregular burning. Reaction gas in this application means oxygen or oxygen-enriched air.
The situation is made even more difficult by the use of an oxygen lance inside the central jet distributor, according to for instance the U.S. Pat. No. 5,133,801, because the oxygen lance enlarges the central jet distributor, which again enlarges the inner diameter of the annular orifice of the reaction gas discharge when using a directional burner, and thus further restricts the discharge aperture itself.
Our U.S. Pat. No. 4,490,170 describes a method where the annular orifice is replaced by several pipes, in which case the harmful asymmetry of the annular orifice, owing to a shift of the central pipe, cannot take place.
A fairly common requirement for the burner is that it must be able to operate in a wide range of capacity and oxygen enrichment. Thus, when using a burner with a fixed aperture, the discharge velocities of the reaction gas fall outside the acceptable range, i.e. an adjustable cross-sectional area is required for the aperture.
The adjusting of the reaction gas introduced in the U.S. Pat. No. 4,331,087 relates to the adjusting of the circulation, and consequently a linear gas velocity mainly parallel to the reaction shaft cannot be adjusted thereby.
The method and apparatus for adjusting the supply of oxygen and oxygen-enriched air according to the present invention is particularly well applied to the above described concentrate burners, particularly to the concentrate burners of a flash smelting furnace.
According to the invention, the reaction gas flowing from the inlet channel to the combustion chamber is distributed, with the aid of the pressure difference and, when necessary, guide vanes, to the whole area of the adjusting assembly. The adjusting member/members open a suitable number of tubular channels at the required spot, and the pressure difference between the burner chamber and the reaction space forces the process air to the reaction space, distributed in a fashion determined by the adjustment of the adjusting device.
The shifting motion of the adjusting member is transversal with respect to the central axis of the burner chamber-side end of the channels. It can open or close flow apertures to the channels, principally starting from the furnace-side or opposite edge of the channel openings. In this fashion, in the case of a partial load the strength of the gas jet flowed into the furnace can be made stronger either near the central axis or farther away of it. Process conditions determine which manner is more advantageous to apply.
The desired velocity of discharge and distribution around the pulverous concentrate flow even with remarkable fluctuations of capacity and oxygen percentage is in our invention obtained with a number of mainly parallel tubes of the desired size, whereto either one or several gases can be conducted, and which suitably encircle the fuel. For adjustment purposes, the tubes can be closed either completely or partially.
The adjusting idea must be sufficiently simple and secure in operation, considering the severe circumstances prevailing in the reaction shaft: high temperature, possible formation of buildups etc.
In all simplicity, the apparatus of the invention is as follows:
adjustment with a uniform adjusting member PA0 adjustment by cutting the adjusting member into separately adjustable parts PA0 a system adjusted according to the passing of time, which sequentially arranges a predetermined flow situation on different sides of the burner PA0 structures made of simple standard materials which endure high temperatures, too PA0 a simple, compact structure (use of oxygen) PA0 observation and cleaning conduits are easily provided PA0 the structure of the adjusting assembly can be made so compact, that it also serves as a closing valve PA0 if a less compact structure is used, there is arranged an automatic cooling for those parts that are exposed to furnace radiation PA0 by using two or more burner chambers, for instance air and oxygen can be driven to the reaction space along separate, individual channels, and an effective mixing can still be achieved in the reaction space proper PA0 the apparatus can be used either with or without a distributor.